Control system for bathers

ABSTRACT

A control system for bathers includes an electronic controller which controls operation of an electric heater assembly connected in a water flow path for heating water. The heater assembly includes a heater housing and electric heater element. A solid state water temperature sensor apparatus provides electrical temperature signals to the controller indicative of water temperature at separated first and second locations on or within the heater housing. The presence of water in the heater housing is detected electronically, by turning on the heater, and monitoring the temperature sensors for unusual temperature rises or other faults for a period of time thereafter. A solid state water presence sensor apparatus can also be used to determine the presence of water within the heater housing, providing electrical water presence signals to the controller indicative of the presence or absence of a body of water within the heater housing. An independent circuit apparatus is connected to the water temperature sensor apparatus and to a power relay, automatically causing high voltage power to be disconnected from the heater assembly when the water temperature exceeds a predetermined temperature. The independent circuit apparatus requiring a manual reset once the water temperature has dropped below a predetermined level to allow the high voltage power to be reconnected to the heater assembly. The system includes ground continuity detection, ground current detection and ground fault detection circuits.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/099,201, filed Sep. 3, 1998, the entire contents ofwhich are incorporated herein by this reference.

[0002] This application is related to co-pending application Ser. No.______, filed concurrently herewith, CONTROL SYSTEM FOR BATHERS WITHGROUND CONTINUITY AND GROUND FAULT DETECTION, by David J. Cline et al.,the entire contents of which are incorporated herein by this reference.

TECHNICAL FIELD OF THE INVENTION

[0003] This invention relates to control systems for bathing systemssuch as portable spas.

BACKGROUND OF THE INVENTION

[0004] A bathing system such as a spa typically includes a vessel forholding water, pumps, a blower, a light, a heater and a control formanaging these features. The control usually includes a control paneland a series of switches which connect to the various components withelectrical wire. Sensors then detect water temperature and water flowparameters, and feed this information into a microprocessor whichoperates the pumps and heater in accordance with programming. U.S. Pat.Nos. 5,361,215, 5,559,720 and 5,550,753 show various methods ofimplementing a microprocessor based spa control system.

[0005] For a properly designed system, the safety of the user and theequipment is important, and is typically concerned with the eliminationof shock hazard through effective insulation and isolated circuity,which prevents normal supply voltage from reaching the user. Examples ofisolation systems for spa side electronic control panels are describedin U.S. Pat. Nos. 4,618,797 and 5,332,944.

[0006] The design of a system to control spas is complicated by the factthat there are electrical components in direct contact with the spawater. These electrical components, such as the heater, pumps, lightsand blower are required to operate with precision and safety. If amalfunction occurs, it should be detected immediately and the spa shutdown to protect the safety of the bather.

[0007] The accuracy of the temperature of the spa water is alsoimportant to the safety and comfort of the spa users. This temperaturecan vary depending on the number of bathers, the amount of insulationwhich is used in the construction of the spa, the operation of the pumpsand blowers, and the outside temperature surrounding the spa.

[0008] When in continuous use, the spa temperature is controlled bytemperature sensors which measure the temperature of the water, andselectively activate a pump to circulate water, and a heater whichraises the water to the temperature set by the user at the controlpanel. There has not in the past been an effective method of accuratelymeasuring and displaying the temperature of the spa if at least one ofthe various temperature sensors are not located at the spa, in directcontact with the water in the bathing vessel. The consequence of this isthat the assembly of the control system into the spa is complicated andexpensive, and requires special attention to the location, insulationand protection of the temperature sensors to achieve satisfactoryresults.

[0009] In normal service, a spa is kept continuously energized, andenergy utilization is high during this time. However, bathers aretypically in the spa water less than 5% of the daily time the spa is inplace. At times when the spa is not in continuous use, the user may wantto maintain a temperature close to use temperature, i.e. in an “almostready” condition, so the spa may be quickly prepared for use by thebather. During this “almost ready” time, and while the owner is awayfrom the spa site, e.g. on vacation, there is a need to maintain thewater sanitation quality, and the temperature may be maintained at alower level to conserve heat energy and therefore electrical energy. Itwould be advantageous if the spa computer system could record andpredict the habits of the bather, and provide an optimum temperaturemaintenance based on the frequency of high and low usage. It wouldfurther be advantageous for the computer system to be able to predictthe rate at which heat is lost and manage the pump and heater operationsfor optimum energy conservation, also reducing mechanical wear and tearon these components. These features are unknown and unavailable in knownspa systems.

[0010] Because of the potentially corrosive nature of the spa water, andthe possibility of the loss of the pump function due to pump failure,the system should have redundant systems to prevent damage to theheating element in the case of pump failure or water flow blockage. Theuse of mechanical devices such as pressure switches which respond to thepressure developed by pump outlet when the pump is activated, are proneto mechanical failure, corrosion failure and leaks. Flow switches whichrespond to the flow of water through a pipe or tube tend to beexpensive, and subject to failure due to hair and foreign materialswrapping around the activating system, requiring frequent service.Pressure switches, currently the most popular method of water flowdetection, can give false readings, are subject to damage anddeterioration and often require calibration.

[0011] An additional hazard represented by the close proximity ofelectrical energy to the bathers, is a significant safety hazard to theuser if the spa is not properly constructed and installed. The integrityof the ground earth system, which protects the spa user in case of anelectrical failure of the heater element insulation system is important.Additionally, the control system preferably has an ability to detect andrespond to a failure of the insulation system, and actively protect theuser by disconnecting the device which has failed.

[0012] As systems controlled by microprocessors or other electroniccontrols can break down, be damaged by voltage surges, or fail throughvarious component malfunctions, it would be highly desirable to have aredundant mechanism to protect from an overtemperature condition andshut down the system completely. This hardware high limit preferablywould have the characteristic of tripping only once, and remaining inthe off position, even after power down and repowering, but beresettable conveniently by the user without exposure to the high voltagewiring of the spa electrical system.

[0013] The control method of some conventional systems is subject toshort cycling or rapid on-off pump activations because the location ofthe temperature sensors can cool off more quickly than the spa water.

[0014] Typical known spa control systems have employed a mechanicalpressure switch or a mechanical flow switch which are subject tocalibration failure, or mechanical breakdown. These random failures aredifficult to repair, and present a considerable inconvenience to theuser, since a spa is too large to move and must be repaired by a spaservice technician.

[0015] Known spa control systems do not teach or use a method ortechnique of protecting the user from electric shock when the insulationof the electrical heater element is damaged and breached and the liveelectrical current is exposed to the bather's water and the ground lineis absent.

[0016] A ground fault circuit interrupter (GFCI) is employed in typicalspa systems which is remotely mounted in the power supply line to thespa. This GFCI must be tested by the user before each use to insure thatit is functional. presenting an inconvenience.

SUMMARY OF THE INVENTION

[0017] In accordance with an aspect of this invention, techniques ofimproving the reliability and safety of the spa or hot tub aredescribed, whereby the user is protected from the possible overheatingof a spa through the use of a multiple sensor array which automaticallyresponds to the failure of a component and covers the shutdown of thespa heating system before equipment is damaged or personnel are injured.Additionally, a more effective way of managing the set temperature ofthe spa is described, and a far more versatile and reliable method ofheater overtemperature mode is provided.

[0018] A further aspect of this invention is a bather's control systemwhich uses a plurality of temperature sensors to provide temperaturemeasurement and other data to a microprocessor, each sensor additionallyfeeding temperature information to an individual manually resettablehardware high limit circuit, which operates separately from the computertemperature control system. The temperature sensors are proximatelylocated with respect to the heater, and a computer algorithm preventsshort cycling and provides highly accurate spa temperature control.

[0019] A further aspect of this invention is a control system associatedwith a heater, where water flow through the heater can be from eitherdirection on the outlet side or pressure side of the pump, or fromeither direction on the inlet or suction side of the pump.

[0020] Another aspect of the invention is a method of collecting anddisplaying and acting on temperature data, which improves user safetyand equipment reliability.

[0021] A further aspect is a solid state electrical conductive circuitwhich detects the presence of water in is the heater through electricalsolid state probes in the water, and/or through the use of multipletemperature readings separated by a time interval, thereby eliminatingthe need for mechanical sensors that might fail.

[0022] Another aspect is a technique of preventing short cycling of aspa control when all temperature sensing is accomplished at the heaterof the spa. This is accomplished in an exemplary embodiment through acontrol routine which moves water to the temperature sensor, at whichtime the computer can properly sense the spa water temperature.

[0023] A further aspect is the intelligent selection of whichtemperature sensor to use to control the temperature of the spa.

[0024] A further aspect is a technique for permitting a second pump, notassociated with the heater circulation pump, to be monitored by the highlimit circuits in the spa.

[0025] A further aspect is a technique of managing the energy usage ofthe spa by automatically shifting into a lower temperature maintenancestate at a specified time interval after the last use of the spa by abather.

[0026] Thus, in accordance with one aspect of the invention, a heatingand control system for bathers is described, which includes anelectronic controller. An electric heater assembly is connected in awater flow path for heating water passing therethrough, comprising aheater housing and electric heater element, the controller arranged tocontrol the operation of the heater element. A water temperature sensorapparatus provides electrical temperature signals to the controllerindicative of water temperature at separated first and second locationson or within the heater housing or a combination thereof. The systemfurther includes water presence sensor apparatus to determine thepresence or absence of water within the heater housing.

[0027] In accordance with another aspect, a heating and control systemfor bathers for heating water is described, which includes a controlcircuit board assembly comprising at least one power relay. A highvoltage power supply is connected to the control circuit board assembly.A control panel is provided for inputting user preferences. A heaterassembly includes a heater housing element connected to the controlcircuit board assembly. A first water pump is connected to the controlcircuit board assembly. A microprocessor is coupled to the control paneland to the control circuit board assembly, said microprocessor adaptedto process signals from a plurality of devices providing water parameterinformation and to energize the heater according to user preferences.The devices include water presence sensor apparatus for detecting thepresence of water in the heater housing element, and a water temperaturesensor apparatus for providing electrical temperature signals to thecontroller indicative of water temperature at separated first and secondlocations on or within the heater housing or a combination thereof. Anindependent circuit apparatus is connected to the water temperaturesensor apparatus and to the at least one power relay, for automaticallycausing the high voltage power to be disconnected from the heaterassembly when the water temperature exceeds a predetermined temperature.The independent circuit apparatus requires a manual reset once the watertemperature has dropped below a predetermined level to allow the highvoltage power to be reconnected to the heater assembly.

[0028] In accordance with another aspect of the invention, a spa isdescribed which includes a heating and control system for bathers. Thesystem includes a control circuit board assembly including amicroprocessor, a high voltage power supply connected to the controlcircuit board assembly, a heater assembly connected to the controlcircuit board assembly, water presence sensor apparatus to determine thepresence of water within the heater assembly, a pump for circulatingwater through the heater assembly, at least one temperature sensor forgenerating an electrical signal proportional to water temperaturelocated at the heater, and an electronic controller adapted toselectively activate and deactivate said pump at selected timeintervals.

[0029] A method is described for detecting the presence of water in asystem including a heater element, a heater housing, and amicrocomputer, the microcomputer controlling the heater, at least onetemperature sensor in close proximity to the heater element, thetemperature sensor feeding temperature data to the microcomputer, themethod comprising:

[0030] collecting and storing a first temperature measurement value;

[0031] activating the heater element for a predetermined time interval;

[0032] deactivating the heater element for a selected time interval;

[0033] collecting and storing a second temperature measurement value;

[0034] calculating the difference between the first temperaturemeasurement value and the second temperature measurement value;

[0035] comparing the resulting difference to a predetermined value toestablish the presence or absence of water adjacent the heater element.

BRIEF DESCRIPTION OF THE DRAWING

[0036] These and other features and advantages of the present inventionwill become more apparent from the following detailed description of anexemplary embodiment thereof, as illustrated in the accompanyingdrawings, in which:

[0037]FIG. 1 is a schematic diagram of a system for bathers including avessel for holding bathing water, a control system, and associated watermanagement equipment.

[0038]FIG. 2A is a schematic block diagram of an embodiment of a controlfor a bathing system with various safety and water management features.

[0039]FIG. 2B is an isometric view of an exemplary embodiment of thecontrol circuit board assembly enclosure and attached heater assembly.

[0040]FIG. 3 is an electrical schematic diagram showing one embodimentof a water detection safety and water management electrical circuitsassociated with a system for bathers.

[0041]FIG. 4 is an electrical schematic diagram of one embodiment of aground fault circuit interrupter circuit integrated into a system forbathers.

[0042]FIG. 5 shows a Ground Integrity Detector circuit to detect andidentify a disconnected ground.

[0043]FIG. 6 is a schematic diagram of a Ground Current Detector circuitto identify and detect when current is flowing through the earthgrounding circuit of the spa wiring.

[0044]FIG. 7A is a cross-sectional diagram of a temperature sensorassembly showing the conductive casing and the components therein.

[0045]FIG. 7B is a simplified flow diagram illustrating a technique fordetecting the presence of water in the heater housing.

[0046]FIG. 8 illustrates a partial program structure showing relevantrelationship of a main program block.

[0047]FIG. 9 is a flow diagram illustrative of a panel service programwhich responds to button activation to change operational modes of thespa.

[0048]FIG. 10 is a flow diagram illustrating the operation of a safetycircuit, temperature measurement and water detection method.

[0049]FIG. 11 is a flow diagram illustrating a technique for selfcalibration of temperature sensors and display of error message.

[0050]FIG. 12 is a flow diagram illustrative of a program to monitor asafety circuit, temperature rate of rise, GFCI and temperature sensorshort/open detection.

[0051]FIG. 13 is a flow diagram of a standard mode of operation of aprogram for intelligent, temperature maintenance using rate of heat lossto drive sampling frequency schedule.

[0052]FIG. 14 is a flow diagram of an economy mode of operation of aprogram for temperature management.

[0053]FIG. 15 is a flow diagram of a standby mode of operation of aprogram for temperature management.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054]FIG. 1 illustrates an overall block diagram of a spa system withtypical equipment and plumbing installed. The system includes a spa 1for bathers with water, and a control system 2 to activate and managethe various parameters of the spa. Connected to the spa 1 through aseries of plumbing lines 13 are pumps 4 and 5 for pumping water, askimmer 12 for cleaning the surface of the spa, a filter 20 for removingparticulate impurities in the water, an air blower 6 for deliveringtherapy bubbles to the spa through air pipe 19, and an electric heater 3for maintaining the temperature of the spa at a temperature set by theuser. The heater 3 in this embodiment is an electric heater, but a gasheater can be used for this purpose also. Generally, a light 7 isprovided for internal illumination of the water.

[0055] Service voltage power is supplied to the spa control system atelectrical service wiring 15, which can be 120V or 240V single phase 60cycle, 220V single phase 50 cycle, or any other generally accepted powerservice suitable for commercial or residential service. An earth ground16 is connected to the control system and there through to allelectrical components which carry service voltage power and all metalparts. Electrically connected to the control system through respectivecables 9 and 11 are the control panels 8 and 10. All components poweredby the control system are connected by cables 14 suitable for carryingappropriate levels of voltage and current to properly operate the spa.

[0056] Water is drawn to the plumbing system generally through theskimmer 12 or suction fittings 17, and discharged back into the spathrough therapy jets 18.

[0057] An exemplary embodiment of the electronic control system isillustrated in schematic form in FIG. 2A. The control system circuitassembly board is housed in a protective metallic enclosure 200, asillustrated in FIG. 2B. The heater assembly 3 is attached to theenclosure 200, and includes inlet/outlet ports 3A, 3B with couplings forconnection to the spa water pipe system.

[0058] As shown in FIG. 2A, the electronic control system 2 includes avariety of electrical components generally disposed on a circuit board23 and connected to the service voltage power connection 15. Earthground 16 is brought within the enclosure 200 of the electronic controlsystem and is attached to a common collection point.

[0059] Adjacent to the circuit board 23 and connected via an electricalplug, a power and isolation transformer 24 is provided. This transformerconverts the service line power from high voltage with respect to earthground to low voltage, fully isolated from the service line power by avariety of methods well known in the art.

[0060] Also provided on the circuit board 23, in this exemplaryembodiment, is a control system computer 35, e.g. a microcomputer suchas a Pic 16C65A CMOS microcomputer marketed by Microchip, which acceptsinformation from a variety of sensors and acts on the information,thereby operating according to instructions described more fully in FIG.14. The invention is not limited to the use of a controller including amicrocomputer or microprocessor, whose functions can instead beperformed by other circuitry, including, by way of example only, anASIC, or by discrete logic circuitry.

[0061] One output of the computer 35 is displayed on the control panel 8through a character display system rendered optically visible bytechnology generally known in the art. Tactile sensors 22 are providedto convert user instructions to computer readable format which isreturned to the control system computer 35 via cable 9.

[0062] The equipment necessary to heat and manage the water quality,i.e. the heater system 3, pumps 5 and 6, blower 4 and light 7, areconnected via electrical cables 14 to relays 36, 126, 129 and 130 on thecircuit board 23, which function under the control of relay drivers 34,selectively driven by the microcomputer 35. These relays and relaydrivers function as electrically controlled switches to operate thepowered devices, and are accomplished by methods well known in the artand provide electrical isolation from the service voltage power for thelow voltage control circuitry. Of course, other types of switchingdevices can alternatively be employed, such as SCRs and triacs.

[0063] Referring now to FIG. 3, also arrayed upon the circuit board andintegral thereto in this exemplary embodiment are several safetycircuits, which protect the system in case of error or failure of thecomponents. Shown in the functional schematic diagram of FIG. 3 is theheater system 3, which includes a generally tubular metal housing 3Aconstructed of a corrosion resistant material such as 316 stainlesssteel, a heater element 42 for heating the water, a heater powerconnection 37 from heater relays to the terminal of the heater element,and sensors 31 and 32 connected through lines 40 to appropriate circuityon the circuit board. These sensors are connected on the circuit boardto both a hardware high limit circuit 33 (FIG. 2A) and to the computercontrol circuit 35.

[0064] A torroid 30, constructed in accordance with techniques wellknown in the art, is provided through which the earth ground connection16 from the heater housing and any other ground connection in the systempasses. This torroid is electrically connected by cable 41 to the groundcurrent detector circuitry 29 which is more fully described in FIG. 6.The output of the ground current detector (GCD) is provided to thecomputer system 35 via an electrical connection through the signalconditioning circuitry.

[0065] The service voltage power is provided to the system through thecenter of a pair of conventional torroids 25 and 26. The electricaloutputs of these torroids are connected to a ground fault circuitinterrupter circuit 27 by electrical connections shown as 38 and 39. Theground fault circuit interrupter is described more fully in FIG. 4. Theground fault circuit interrupter feeds a signal to the computer 35,which tells the computer of a ground fault existence. Testing of theground fault circuit interrupter is managed by the computer on a regularbasis, and an exemplary program algorithm of this activity isillustrated in FIG. 11.

[0066] A ground integrity detector 28 is provided which is more fullydescribed in FIG. 5. The ground integrity detector is attached to theearth ground 16 and provides a signal to the computer control 35. Ifmore than one earth ground is used in a particular application, anotherground integrity detector could be used in accordance with the inventionto verify the ground continuity.

[0067]FIG. 3 is a schematic diagram of a temperature sensing system fora spa, and comprises the control system. Heater assembly 3 has a heatershell 3A, most usually made of metal, but can also be constructed ofconductive plastic or of plastic with an internal metallic ground plate.Confined within the heater shell is a heater element 43, constructed toprovide insulation from the water as generally known in the art. Poweris provided to the heater element from connection points 124 and 127.This power is provided responsively to the programmed temperatureprovided to the microcomputer 35 through control panel 22 as isgenerally known from the prior art.

[0068] In this exemplary embodiment, the heater housing 50 is tubular inshape. However, other shapes come within the scope of this inventionprovided they have an inlet and an outlet. Located close to each end ofthe heater element are temperature sensor assemblies. These assembliesinclude thermistors 133 and 134, which are usually of a negativetemperature coefficient (d). However, they can be positive temperaturecoefficient thermistors, thermocouples or any other temperaturesensitive means. The temperature sensor is generally potted in epoxy orthe like, in stainless steel housings 31 and 32. The stainless steelhousings are mounted into the side of the heater assembly withinsulating collars, which provides a water pressure seal and aninsulative barrier from the heater housing. However, when water ispresent, there is a conductive path which can be detected by theassociated circuitry. This conductive path extends from sensor housing32 to sensor housing 31 through the water in the housing. Whenmicrocomputer 35 sets the output high through resistor pair 78, 79,current travels through connecting wires 141, 143 and the sensorhousings 31A, 32A, water between the sensor housings, and voltagedivider network created by resistor pair 80, 81, resistor 84, resistorpair 82, 83 and resistor 91. The resulting voltage is buffered to themicrocomputer by op amp 90, which is powered and installed according toknown techniques.

[0069]FIG. 7A illustrates in cross-section an exemplary one of thetemperature sensor assemblies 31, 33. The assembly 31 includes astainless steel or other corrosion-resistant housing 31A, which ismounted into the heater housing using an insulative bushing 31B. Thebushing is fabricated of a dielectric material, for example, KYNAR (TM)or polyprophylene, thus electrically insulating the housing 31A from theheater housing. The bushing 31B can have a threaded peripheral surface(as shown) which is threaded into a correspondingly threaded opening inthe heater housing. Alternatively or in addition, the bushing can besealed into the opening with a non-conductive adhesive. The thermistor133 is mounted at a distal end of the housing 31A, to be positionedwithin the heater housing in close proximity to the water flow throughthe heater housing. Wires 144 provide an electrical connection to thethermistor from the circuit 2. A third wire 143 is passed into thehousing 31A from circuit 2, and is electrically connected to the housing31A, e.g. by a solder connection. This connection (wire 143) is used inthe water presence detection process. The elements 133 and 143-144 arepotted with a potting compound such as epoxy.

[0070] In operation previously described, the water detection system isnormally held in a low state by the microcomputer output, which isturned off. When the microcomputer program turns the output on, orswitches to a high state, if no water is present to form a conductivepath, no change is detected at the output of op amp 90. However, ifwater is present, then the output of 90 changes state in response tostate change of the output because of the conductive characteristic ofwater under electrical current. This circuit is activated for very shortperiods of time and then returned to an inactive or grounded state. Anexemplary effective cycle could be for 5 milliseconds every 100milliseconds. In addition, it may be advisable to change polarity oneach sensor to prevent corrosion damaging one sensor to the point ofdestruction.

[0071]FIGS. 3 and 7A thus illustrate a combination sensor which uses thehousing of the temperature sensor for the water presence detector. Aseparate pair of electrodes distinct from the temperature sensor is alsowithin the scope of this invention, as is the concept of using the shellof the heater housing for one electrode, and an insulated, conductiveprobe, both hooked to a resistor divider network, as previouslydescribed.

[0072] Since the water presence detector has no moving parts, water mayenter the heater housing from either end and flow out the other end.Generally, a pump has an inlet, or suction side, and an outlet, orpressure side. The heater assembly fitted with the water presencedetector may therefore be fitted to either the suction or outlet side ofthe pump with equally satisfactory results. This flexibility isextremely valuable, as it allows exceptional latitude in the principallayout configuration of the pump and heater components for assembly intothe spa. Temperature information regarding the heater is gained throughsensor thermistors 134 and 133, formed and placed generally adjacent tothe heater element, and on either end of the heater element. As thethermistors change resistance in response to the immediate temperaturesurrounding, an electrical signal is generated at the output of op amps97 and 89, through associated electrical circuitry. Resistors 88, 85 andcapacitors 87 and 86 are configured to provide the current form ofelectrical input to provide a sensible voltage through the op amp. Eachtemperature sensor is configured in like manner. When water is flowingin the heater assembly, both temperature sensors will reach equilibriumand provide a proportionally equal voltage if the heater element 42 isnot activated.

[0073] Under control of the microcomputer, if the heater element isenergized, the physical location of the temperature sensors may thendetect a different temperature of water between the inlet and the outletof the heater housing. Depending on the actual set temperature of thecontroller, the microcomputer will elect to use the temperature of thelower, or inlet side sensor, as the actual temperature of the spa, andturn off the heater when the temperature of the spa is equal to thedesired temperature of the spa.

[0074] If the water flow slows down to a point where there is asubstantial difference between the inlet and outlet temperature, thenthe microcomputer can interpret this as a trouble signal and deactivatethe heater. Further, if there is a blockage in the plumbing, or the pumpfails to circulate water, the temperature in the heater housing may riseto unacceptable limits. Accordingly, op amps 105 and 104, not feedinginto the microcomputer, but entirely independent circuit have areference network of resistors which provides a precision referencevoltage. When the input to either of the op amps 104, 105 exceeds theprecision reference voltage, the output of the op amp swingsappropriately to deactivate transistor 133 thereby causing gate 118 tochange state, and causing relay driver 131 to turn off heater relays 130and 129. The heater is therefore shut off and can only be reactivated bya manual reset signal from control panel 22, through the microcomputer,which changes state of gate 118. However, as long as either temperaturesensor remains above a temperature set by the reference voltagenetworks, the manual reset signal cannot work. An exemplary appropriatetemperature for the high limit circuit deactivation is between 118° F.and 122° F. to protect from injury. As long as a manual reset signal isnot given, the circuit will remain in an off state.

[0075] Each described circuit is sensibly connected to the microcomputer35, which has electrical inputs responsive to changes in voltage levelfrom a logic high to a logic low. An exemplary embodiment employs arelatively sophisticated microcomputer, and 8 bit microcomputers andmore powerful microcomputers can be employed. Typically an embodiment ofthis invention would employ a CMOS or complimentary metal oxide versionof a microcomputer.

[0076] Because the temperature sensors 31 and 32 generate a voltageproportional to temperature, a device such as an analog to digitalconverter 99 is used to convert the analog voltage to a readily usabledigital value which is provided at the microcomputer via customarymeans. In a preferred embodiment, the temperature measurement componentsare thermistors which are matched in their resistance versus temperaturevalues. Typically, accuracies are available of 0.2° C. precision,meaning two thermistors held at a precise resistance value by varyingthe temperature of each independently will match within 0.2° C. of anequal temperature. By using thermistors of no more than 1° C. precision,the system will not require calibration of the hardware interface of theelectrical signal of the thermistor temperature output. In addition, ifthe computer is able to circulate water through the system withoutactivating the heater, the temperature sensors will be in the sametemperature environment. Therefore, the computer will able to comparethe readings of the sensors to determine if they are within theprecision specified above, 1° C., and provide a software calibration forfinal correction.

[0077] An additional or alternative technique for sensing the presenceof water in the heater housing is illustrated in the flow diagram ofFIG. 7B. This embodiment senses the water flow, which will tend to coolthe heater and temperature sensor assemblies. In the absence of water orwater flow, with the heater energized, the temperature sensors willdetect a significantly increased rate of temperature rise. This can thenbe used to determine that no water is present or that components havefailed (e.g., water pump failure). While the water pump 1 is activated,the microprocessor 35 may activate the heater 3 for a selected period oftime, say 4 seconds, deactivate the heater for a selected period oftime, say one minute, and compare the temperature readings before theactivation began to the readings after the selected off time interval.If the temperature difference exceeds a predetermined amount, say 10degrees, then the heater can be determined by the microprocessor to haveno water present in the housing. This technique is illustrated in FIG.7B with a an operational subroutine executed by the microprocessor. Thewater pump is activated during the steps 350-356. At step 350, a firsttemperature reading at both of the temperature sensors is taken with theheater off. Then, the heater is turned on for a predetermined timeinterval (step 353) and then turned off. After another time interval haselapsed (step 354), a second temperature reading is taken (step 356).The difference between the two readings for each temperature sensor isthen taken, and compared to a threshold (step 358). If the differencefor either sensor is greater than this threshold, then themicroprocessor declares that no water is present or that there is acomponent failure (step 360). If the difference is not greater than thethreshold, the microprocessor determines (step 362) whether any otherfaults have been detected, such as too large a differential between thetemperature readings taken at the two sensors 31, 33 (described morefully below). If so, the operation branches to step 360. Otherwise, themicroprocessor will determine that water is present in the heaterhousing (step 364).

[0078] Shown in FIG. 4 is a Ground Fault Circuit Interrupter (GFCI)circuit. This electrical circuit is configured to be in closerelationship with the electrical system which controls the spaequipment. The main power supply which supplies the current to the spaequipment and control is shown at 15, and passes through two torroids,shown at 25 and 26. As long as the net current flowing through thetorroids is equal, the torroids see a no magnetic flux. However, if adevice, such as a heater element fails, some current escapes through theearth ground, as at 16.

[0079] When an imbalance occurs, an electromagnetic coupling occurswhich sets up an electrical current in the sense circuit 150 associatedwith the detection torroids. The circuit 150 outputs a fault or errorsignal proportional to current flow which is provided to themicrocomputer (via analog-to-digital conversion, not shown in FIG. 4).The microcomputer then responds with an error message which is displayedon the control panel 22. In addition, a fault creates a change in stateat output connection 116, which connects to 117 on FIG. 3. Thisconnection activates the circuits generally beginning at diode 109. Thisin turn triggers transistor 133. Gate 118 changes state in response,deactivating relay driver 131 and opening relays 129 and 130d.Microcomputer 35 also opens all other relays, 36, disconnecting anyother components, such as pumps, blowers and lights.

[0080] Microcomputer 35 can test the functionality of the GFCI circuitby outputting a signal through resistor 56, which activates transistor54, closing relay 52. Current passes through resistor 23, bypassingtorroids 25 and 26, imbalancing the current flowing through thetorroids. This causes GFCI circuitry to trigger, providing a signal tomicrocomputer 35 that the circuit has properly triggered. When themicrocomputer senses a trigger signal, it resets test relay 52 byrestoring status to resistor 56. Because a GFCI fault triggers the highlimit relays 129 and 130, opening them up, the microcomputer alsogenerates a system reset signal on line 198 which re-enables the driverswhich activate the relays 129 and 130. This sequence of events iscarried on periodically, such as once per day, to verify thefunctionality of the GFCI circuit. Generally, a real time clock,functioning as a master timekeeper, would provide a reference signal anda programmed interval between tests, such as 24 hours could be set usingtechniques known by ones skilled in the art of microcomputerprogramming.

[0081]FIG. 5 illustrates a Ground Integrity Detector (GID) device. TheGround Integrity Detector includes a neon bulb 20 connected in serieswith a limiting resistor 43 from the power service voltage to the systemearth ground 16. If the ground is properly connected, current will flowfrom the supply, through the limiting resistor. The current flow can belimited to less than one milliampere (ma). The light from the neon bulbis contained in a light tight enclosure 28, which also contains anopto-resistive device which falls in resistance in the presence oflight. By connecting this opto-resistive device in a resistor dividercircuit, shown generally at 46, a signal indicating the presence oflight and therefore of a good ground, can be presented to the computercontrol system. The computer control system then manages thisinformation according to instructions more fully described in FIG. 11.

[0082] Shown at FIG. 6 is a Ground Current Detector (GCD). The groundcurrent detector is shown as capable of detecting currents which mightflow in a ground attached to a heater current collector or shell 50which is part of the heater assembly 3, including a heater element 42,and any other device powered or containing line voltage, such as lights,blowers and pumps, and the enclosure itself.

[0083] As an example, in normal service, heater elements 42 may fail andrupture due to either mechanical failure, corrosion, or electricalbreakdown. The shell of the heater 50 then collects the current androutes it through the ground line, thereby protecting both the occupantof the spa and the equipment. However, if the current is allowed to flowindefinitely, there is a possibility of health hazard or equipmentdamage occurring. When current flows through the ground line 16, anelectromagnetic coupling occurs between the current and the torroid 30through which it passes. This coupling creates a voltage proportional tothe current, and if the current is an AC current, an AC voltage will beinduced in the torroid. When this voltage is provided to a full waverectifier comprising sense circuit 152, a rectified DC signal iscreated. After conditioning this rectified DC signal with a capacitor 48and resistor 49, a DC signal is generated proportional to current flow.(Alternatively, circuit 152 with its full wave rectifier can be replacedwith a sense circuit similar to circuit 150 (FIG. 4), producing an errorsignal proportional to current flow.) When no current is flowing, thebleed resistor 50 insulates the circuit from the electrical noise. Thecomputer control 35 consistently monitors the state of the input signalline from the GCD circuit. If a ground current is detected, the computerresponds in accordance with instructions more fully explained in FIG. 11to shut off the relays 36 through relay drivers 34 to reduce hazards toequipment and personnel.

[0084] Referring now to computer flow diagrams at FIGS. 8-13, thefunctional interrelation of the various prior described components isdisclosed. These flow diagrams illustrate the action which is directedby the computer 35, as shown on FIG. 2A, responding to signals generatedfrom the control panel 22 through interconnect cable 9. Themicroprocessor is programmed to accomplish the functions illustratedtherein.

[0085] As shown in FIG. 8 in block form, and more fully disclosed inFIGS. 9-14, the spa control system computer is constantly running asafety and error detection program. At any time in this program, acontrol panel signal can interrupt the program, branching off into thepanel service program. When the mode button is pressed, the programbranches into the “mode selection” routine, shown in FIG. 10. In themode selection routine, one of three modes is selected, standard,economy or standby. Once a time interval has passed without furtherbutton presses, typically 3 seconds, the program reverts back to thesafety program, looping through the proper “mode” program also. When thecontrol system is first energized, it is default programmed to start inthe economy (econ) mode.

[0086] To more fully describe the process diagrammed, the steps aredescribed below.

FIG. 10

[0087] Step 225. Starting point of the program for flow chart purposes.Program normally initializes by known means to clear and reset allregisters upon power up.

[0088] Step 226. Check for presence of water in heater. If none, branchto 227, otherwise branch to 228.

[0089] Step 227. Disable heater and loop back to 226.

[0090] Step 228. Check for software set high limit of 118° F. Iftemperature at either temperature sensor exceeds this value, the heateris turned off. If less than 118° F., program loops to 232.

[0091] Step 229. Turn heater off.

[0092] Step 230. Display error message on control panel 8 of OH2 tosignify overheat—at least 118° F.

[0093] Step 231. Remeasure temperature sensor. If temperature exceeds116° F., program loops back to Step 229. If less than 116° F., programloops to Step 228.

[0094] Step 232. Check for hardware high limit, if tripped branch to233, otherwise 237.

[0095] Step 233. Shut down system.

[0096] Step 234. Display error condition “OH3” for overheat hardwarehigh limit.

[0097] Step 235. Measure water temperature. If less than 116° F., thenbranch to 236, otherwise branch to 233.

[0098] Step 236. Check for control panel input. If any button ispressed, system will reset.

[0099] Step 237. If water temperature is over 112° F., branch to 238,otherwise go to 241.

[0100] Step 238. Turn off everything—branch to 239.

[0101] Step 239. Display system error message “OH1” for overheat of atleast 112° F.

[0102] Step 240. Remeasure water temperature, if less than 110° F.,branch to 240, otherwise branch to 241.

[0103] Step 241. Check for balance between water temperature sensors. Ifa difference of greater than 5° F. exists, branch to 242, otherwisebranch to 244.

[0104] Step 242. Turn heater off. Branch to 243.

[0105] Step 243. Display error message HFL, meaning the water flow inthe heater is too low. Branch to 241.

[0106] Step 244. Proceed to 273.

FIG. 11

[0107] Step 273. If the heater is on, proceed to 274. If not, proceed to340.

[0108] Step 340. Measure output of temperature sensor 1.

[0109] Step 341. Measure output of temperature sensor 2.

[0110] Step 342. Subtract lowest value from highest value.

[0111] Step 343. If the result is less than or equal to 1° F., thenproceed to 345, otherwise proceed to 344.

[0112] Step 344. Send error message “CAL” to display on control panel.Proceed to 274.

[0113] Step 345. Store result in lowest sensor value register.

[0114] Step 346. Add contents of calibration register to all temperaturemeasurement operations. Proceed to 274.

FIG. 12

[0115] Step 250. Has either sensor changed temperature more than 2°F./second? If so, proceed to 251, otherwise proceed to 253.

[0116] Step 251. Turn off heater, proceed to 252.

[0117] Step 252. Display “HTH1” error message for heater imbalance.Proceed to 250.

[0118] Step 253. Check proper input for ground integrity, that is, isthe ground properly connected. If not, proceed to 254, otherwise branchto 256.

[0119] Step 254. Turn off system, proceed to 255.

[0120] Step 255. Display error message GR for ground disconnected or notproperly hooked up. Proceed to 253.

[0121] Step 256. Check for ground leakage current. If none, proceed to245. If yes, branch to 257.

[0122] Step 245. Is GFCI tripped? No, branch to 259. If yes, branch to246.

[0123] Step 246. Shut down system and open all relays. Proceed to 247.

[0124] Step 247. Display GFCI error message indicating there is a groundcircuit fault. Proceed to 248.

[0125] Step 248. Has system reset been pressed from control panel? Ifyes, loop to 245, otherwise loop to 247.

[0126] Step 257. Turn everything off. Proceed to 258.

[0127] Step 258. Display GRL error message to indicate ground leakagedetected, proceed to 256.

[0128] Step 259. Check real time clock. If time is equal to 2:00 am,branch to 260, otherwise proceed to 266.

[0129] Step 260. Test ground fault interrupter circuit by closing relayto imbalance current in power supply.

[0130] Step 261. Check for GFCI system trip. If yes, proceed to 263, ifno branch to 262.

[0131] Step 262. Turn off system, proceed to 265.

[0132] Step 265. Display error message GFCF for ground fault interruptercircuit failure, proceed to 261.

[0133] Step 263. Reset GFCI circuit via microprocessor reset, proceed to264.

[0134] Step 264. Reset hi-limit circuit via microprocessor output.Branch to 266.

[0135] Step 266. Is either temperature sensor disconnected? If yes, 267.If no, 269.

[0136] Step 267. Turn everything off, proceed to 268.

[0137] Step 268. Display SND, loop to 266.

[0138] Step 269. Is either temperature sensor shorted? If yes, proceedto 270. If no, 275.

[0139] Step 270. Turn off system, proceed to 271.

[0140] Step 271. Display error message SNS. Loop to 269.

[0141] Step 275. Proceed to mode as selected by panel service program.

FIG. 13

[0142] Step 276. Program checks for function of pump 1 which circulateswater through heater. If pump is already on, program proceeds to 282,otherwise program proceeds to 277.

[0143] Step 277. Check for 30 minute elapsed time. If pump has been offfor less than 30 minutes, branch back to main safety program at 225. Ifpump has been off for 30 minutes, proceed to 227.

[0144] Step 278. If water temperature has dropped more than 1° F. belowset temperature in the last hour, proceed to 281, if not, proceed to279.

[0145] Step 279. Reset iteration counter to zero and proceed to 280.

[0146] Step 280. Reset 30 minute pump off timer and proceed to 225 mainsafety program.

[0147] Step 281. Turn pump on, proceed to 282.

[0148] Step 282. Allow pump to run for 30 seconds. If not, look back tomain safety program 225. If so, proceed to 283.

[0149] Step 283. Read water temperature, proceed to 284.

[0150] Step 284. Check to see if 5 seconds has passed from beginning ofwater temperature read. If so, proceed to 285, otherwise loop back to283.

[0151] Step 285. Compare water temperature to set temperature. If watertemperature higher than set temperature, proceed to 286. If not, proceedto 287.

[0152] Step 286. Increment iteration counter, proceed to 290.

[0153] Step 287. If water temperature is more than 1° F. below settemperature, proceed to 288, otherwise proceed to 286.

[0154] Step 288. Reset iteration counters. Proceed to 289.

[0155] Step 289. Turn on heater, proceed to 225.

[0156] Step 290. Turn off heater, Proceed to 290.

[0157] Step 291. Turn off pump. Proceed to 294.

[0158] Step 294. Display last valid temperature. Proceed to 280.

[0159] Step 280. Reset 30 minute pump off timer. Proceed to 292.

[0160] Step 292. Has a button on control panel been pressed in the last24 hours? If yes, branch to 225. If not, branch to 293.

[0161] Step 293. Shift to economy mode. Proceed to 225.

[0162] Step 225. Proceed to Safety Circuit Chart A.

FIG. 14

[0163] Step 275. Once selected by “mode” selection, main safety programbranches into economy mode and proceeds to 300.

[0164] Step 300. Program checks for filter cycle. If filter pump is on,program branches to 301, otherwise to 225.

[0165] Step 301. Read temperature 1 and store.

[0166] Step 302. Read temperature 2 and store.

[0167] Step 303. Select lowest of the two temperature readings.

[0168] Step 304. If spa water temperature is equal or greater than settemperature, branch to 305; otherwise branch to 306.

[0169] Step 305. Turn heater off, proceed to 310.

[0170] Step 310. Display last valid temperature. Proceed to 308.

[0171] Step 306. Is spa more than 0.1 degree below set temperature? Ifyes, branch to 307, otherwise branch to 310.

[0172] Step 307. Turn heater on. Proceed to 310.

[0173] Step 308. Has a control panel button been pressed in the last 24hours? If yes, branch to 225. If not, branch to 309.

[0174] Step 309. Shift to standby mode and proceed to 225.

FIG. 15

[0175] Step 275. Once selected by “mode” selection, main safety programbranches into standby mode and proceeds to 325.

[0176] Step 325. Program checks for filter cycle. If filter pump is on,program branches to 326, otherwise to 225.

[0177] Step 326. Read water temperature 1 and proceed to 327.

[0178] Step 327. Need water temperature 2 and proceed to 328.

[0179] Step 329. Compare spa water temperature to 15 degrees below settemperature. If spa temperature is less than 15 degrees below settemperature, proceed to 328, otherwise 329.

[0180] Step 332. Turn on heater and proceed to 225.

[0181] Step 328. Select lowest of the two temperature readings andproceed to 329.

[0182] As can be seen from the foregoing specification and drawings, aspa control system is disclosed which is self contained with a pluralityof sensors located adjacent the heater element for both temperatureregulation and limiting. In the preferred embodiment, the heater andcontrol system are attached together in adjacent proximity, asillustrated in FIG. 1 and FIG. 2B. This provides the greatest protectionfrom mechanical hazards and facilitates the sensing of criticalparameters, such as water temperature and water presence. In thispreferred embodiment also, a microcomputer is the central processingunit, which receives data from a plurality of sensors in and adjacent tothe heater, which provides data for the intelligent management of theuser's desires. These user's desires are provided to the controlmicrocomputer via control panels which provide a plurality of easyaccess for activating functions and features of the spa.

[0183] Additionally, integrated as a part of the system interconnectboard in the control system, are not only the microcomputer, but alsothe safety circuity which detects and monitors the integrity of thesystem ground. In addition, as shown in FIG. 2A, there is a ground faultcircuit interrupter circuit which shuts down the system when aninsulation failure occurs and there is a short to the bather's water ofvoltage. All of these functions are self-contained within the controlsystem circuitry and heater, and require no other connection thanpumping from or to a pump, power hookup with a ground, and a controlpanel connection.

[0184] In the installation of such a preferred embodiment at thefactory, ease of assembly into the spa is facilitated by eliminatingexternal temperature sensors employed in previously known systems, sincethe sensors are contained within the system enclosure and heaterassembly (FIG. 2B). Also eliminated are any calibration requirements formechanical switches and sensors which might need adjustments. Pumps,blowers and lights are plugably connected to the control system. Theuser is protected from connection to the supply voltage by thecontainment of all electrical components within the heater housing andenclosure structure, which is hooked to earth ground.

[0185] When the control system is initially energized, themicroprocessor checks for presence of water, and if present, starts thepump. As described above, the presence of water can be detected inaccordance with aspects of the invention by either the use of water as aconductor, and detecting the flow of electrical current through thewater, and/or by use of the technique described with respect to FIG. 7B.(Of course, other water detection techniques could also be employed inthe system of FIG. 1, including the conventional mechanical, optical orultrasonic flow sensors.) If the routine of FIG. 7B is repeated at aslow enough cycle rate, the system will not overheat. If repeated loopsthrough this software routine are executed at frequent intervals, and nowater is present, the temperature of one of the temperature sensors willeventually exceed 118° F., and the hardware high limit circuit will shutdown certain aspects of the controller, including the heater as at step228. As an alternative to waiting for the hardware high limit circuit toshut down powered elements, the first detection of a temperaturedifference exceeding a predetermined amount, or the occurrence of otherfaults, can be treated by the controller 35 as a serious faultcondition, with the controller causing shutdown of all output relays(e.g. step 362 of FIG. 7B). The system may be configured to require amanual restart to be returned to normal operation.

[0186] After the water presence test has determined that water ispresent in the heater housing, the microprocessor reads the temperaturesensors, calibrates them, and upon determination that all sub-systems ofthe control system are within tolerance, starts up the heater, ifnecessary. When the spa water reaches the set temperature, the heater isturned off, and once the heater element has cooled down, the pump isturned off. Every selected time period, the pump is started up, drawingwater through the heater and temperature sensor array. If heat is neededto hold the spa water at the desired temperature, the heater is turnedon. If not, then the pump is shut down for a time interval. This timeinterval is adjusted based on the rate of heat loss from the spa. If therate of loss is low, the time interval can be extended to reduce wear onthe pump.

[0187] The spa is generally started in the standard mode, where the settemperature is maintained by the controller as described. When the pumpis not running, the temperatures the sensors read do not necessarilyreflect the actual spa temperature, due to changes in temperature in thespa equipment environment. Therefore, the last known valid temperatureis displayed on the control panel, and it does not change until the pumpstarts up and runs again on its time interval circulation to check spatemperature.

[0188] If the user of the spa has not activated a feature of the spa fora period of time, via the control panel, say 12 hours, the spa canautomatically shift into a lower energy consumption state, shown as“economy,” where the set temperature is only reached when the spa isfiltering. Again, if no activity is experienced at the control panel,the spa can automatically shift into an even lower energy consumptionstate, the “standby” mode. In the “economy” mode, the last known validtemperature is displayed while the filter pump is not running, andactual temperature is displayed when the pump is running. To warn theuser of the mode selection, the display of temperature is alternatedwith the message “econ”.

[0189] When in the standby mode, no temperature is displayed, just themessage “stby”, and the spa pump is filtered on user set or defaultcycles. The heater is activated only to maintain the spa water at 15 to20° F. below the set temperature to reduce energy consumption and theneed for sanitation chemicals.

[0190] At any time, if the proper ground is damaged or removed from thespa, the microprocessor disconnects the peripheral equipment, includingthe heater, and provides an error message to the control panel to warnthe users, and provide a diagnostic message to assist in curing theproblem. This is accomplished by the GID, FIG. 5. If there is an actualshort to ground through the ground wire, the system can be shut down byeither a ground current detector as in FIG. 6, or a ground fault circuitinterrupter, as in FIG. 4.

[0191] If there is an over heat condition, the various softwaredetection methods shut off the heater, but if there is a high limitvalue of over 118-122° F., the system trips the electronic hookup highlimit associated with each temperature sensor. This opens a differentset of relays from the temperature regulation relays, shutting down theheater until the temperature falls below a safe temperature, and thesystem is re-set from the control panel.

[0192] A detailed reference summary for exemplary elements shown in thefigures for the exemplary embodiment follows: FIG. 1 ReferenceDescription  1 Spa with water  2 Electronic control system  3 Heaterassembly  4 Pump 1  5 Pump 2  6 Air blower  7 Light  8 Control panel  9Control panel connecting cable 10 Auxiliary control panel 11 Auxiliarycontrol panel cable 12 Spa skimmer 13 Spa water pumping 14 Electricalcable interconnect 15 Electrical service supple cable 16 Earth ground 17Suction fitting 18 Jet therapy fitting 19 Air blower supply pipe

[0193] FIG. 2A Reference Description 21 Display of information 22 Paneltouch pads 23 Main circuit board 24 Isolation transformer 25 GFCITorroid 1 26 GFCI Torroid 2 27 GFCI circuitry 28 Ground Integrity 29Ground Current Detector 30 GCD Torroid 31 Sensory Assembly 1, temp & H₂Odetect 32 Sensory Assembly 2, temp & H₂O detect 33 High limit circuit 34Relay drivers 35 Microcomputer 36 Relays 37 Heater power interconnect 38GFCI Torroid 1 interconnect 39 GFCI Torroid 2 interconnect 40 Tempsensor interconnect 41 GCD Torroid interconnect 42 Heater element

[0194] FIG. 3 Reference Description  22 Control panel  3 Heater assembly 16 Earth ground 31, 32 Temperature sensor assembly 44, 77 Electricalconnection leads 78, 79, 82, 83 Resistor 430 kohm 80, 81 Resistor 820kohm  84, 115 Resistor 10 kohm 113, 112, 85, 94, 98, 107 Resistor 20kohm 86, 92 Capacitor 0.1 microfarad 87, 93 Capacitor 22 microfarad 88,95 Resistor 2 kohm 122, 89, 97, 104, 105 Op Amp LM324  90 Op Amp LM662 91 Resistor 68 kohm  96, 103 Resistor 1 kohm  99 MC145041 A/D converter110, 118 4081 B Gate 101, 108 12-7 kohm resistor 102, 106 1 meg ohm 109,110, 111 Diode 1N4003 114 Capacitor 1.0 microfarad 140 Diode 1N4754 117Circuit connection to FIG. 4 119 Resistor 4-99 kohm 120 Resistor 6 kohm121 Thermal cutoff 123 LED red. 124 Output to heater 125 Power intoheater 126 Heater relay 127 Output to heater 128 Power into heater 129,130 High limit relay 131, 132 Darlington relay drivers 133 Transistor2N2222

[0195] FIG. 4 Reference Description 25 Torroid 1/200 26 Torroid 1/100035 Computer 52 Relay D&B T90 53, 76 Diode 1N4003 54 Transistor 2N2222 55Resistor 20 K 56 Resistor 2 K 57 Resistor 200 ohm 58 Capacitor 22 uf 59,72 Capacitor .001 uf 60 Resistor 100 kohm 61 Resistor 220 kohm 62, 67Resistor 260 kohm 63, 64, 69, 70 Diode 1N914 65 Operational amplifier4M324 66 Capacitor 33 pf 68 Resistor 3.3 meg ohm 71 Capacitor 0.1 uf 73Resistor 15 K 74 Resistor 470 ohm 75 Capacitor .01 uf 150  Sense circuit

[0196] FIG. 5 Reference Description 43 Neon bulb limiting resistor 44Photo resistor 45 Circuit ground 46 +5 volts 42 Heater element  3 Heaterassembly 50 Heater housing 36 Relays 16 Earth ground 28 Ground integritydetector housing 35 Microcomputer 20 Neon bulb

[0197] FIG. 6 Reference Description 47 Bridge rectifier, 1 amp 48Capacitor, 22 uf 49 Resistor, 10 kohm 50 Heater housing 51 Bleedresistor, 100 kohm 42 Heater element  3 Heater housing 36 Relay 30Torroid 1/1,000 turns 16 Earth ground 34 Relay drivers 45 Circuit ground35 Microcomputer 152  Sense circuit

[0198] FIG. 7A Reference Description  31 temperature sensor assembly 31Asensor housing 31B insulating bushing 142 potting compound 143 wire 144wires

[0199] The embodiments shown are merely illustrative of the presentinvention. Many other examples of the embodiments set forth above andother modifications to the spa control system may be made withoutdeparting from the scope of this invention. It is understood that thedetails shown herein are to be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. A heating and control system for bathers,comprising: an electronic controller; an electric heater assemblyconnected in a water flow path for heating water passing therethrough,comprising a heater housing and electric heater element, the controllerarranged to control the operation of the heater element; watertemperature sensor apparatus providing electrical temperature signals tothe controller indicative of water temperature at separated first andsecond locations on or within said heater housing or a combinationthereof; and water presence sensor apparatus to determine the presenceor absence of water within said heater housing.
 2. A system according toclaim 1 wherein said water presence sensor apparatus is adapted toprovide electrical water presence signals to the controller indicativeof the presence or absence of a body of water within the heater housing.3. A system according to claim 2 wherein the water presence sensorapparatus comprises a solid state sensing device.
 4. A system accordingto claim 3 wherein the solid state sensing device comprises apparatusfor passing an electrical sensing signal through the body of water ifpresent within the heater housing, and a detector circuit to detect saidelectrical sensing signal.
 5. A system according to claim 4, wherein thedetector circuit generates said electrical water presence signalsindicative of the presence or absence of a body of water within theheater housing.
 6. A system according to claim 2, wherein the waterpresence sensor apparatus is adapted to employ the electricalconductivity of a body of water within the heater housing to detect thepresence or absence of the body of water therein.
 7. A system accordingto claim 1, wherein the water presence sensor apparatus is free of anymoving mechanical parts.
 8. A system according to claim 1 wherein thewater presence sensor apparatus comprises the controller, and whereinthe controller is adapted to collect temperature values before and afteroperating the heater assembly for a given time interval, and todetermine whether water is present as a result of the difference in thebefore and after temperature values.
 9. A system according to claim 1wherein the water temperature sensor apparatus comprise a plurality ofsolid state temperature probes.
 10. A system according to claim 1,further including a controller enclosure, and wherein the controllerincludes a controller circuit board within the controller enclosure, andwherein the heater assembly is attached to the controller enclosure. 11.A system according to claim 1, wherein the first location is at oradjacent a water entrance of the heater assembly, and the secondlocation is at or adjacent a water exit of the heater assembly.
 12. Asystem according to claim 1 wherein said controller is adapted toenergize the heater assembly when the temperature sensed at said firstlocation and the temperature sensed at said second temperature locationare within predetermined limits.
 13. A system according to claim 1wherein the controller is further adapted to deactivate operation ofsaid heater assembly if said water temperature sensor apparatus detectsa temperature rate of rise at said first location or at said secondlocation that exceeds a certain specified value.
 14. A system accordingto claim 1 wherein the controller is adapted to compare the respectivetemperatures detected at said first and second locations and to use thelower of said temperatures to control the activation and deactivation ofthe heater.
 15. A system according to claim 1, further comprising a pumpfor circulating water through the heater assembly, the pump controlledby the controller.
 16. A system according to claim 15 wherein the pumphas a water input and a water output, and wherein the water output ofsaid pump is directed into said heater assembly.
 17. A system accordingto claim 15 wherein the water input of said pump is through the heaterassembly.
 18. A heating and control system for bathers for heatingwater, comprising: a control circuit board assembly comprising at leastone power switching device; a high voltage power supply connected tosaid control circuit board assembly; a control panel for inputting userpreferences; a heater assembly comprising a heater housing elementconnected to said control circuit board assembly; a first water pumpconnected to said control circuit board assembly; a microprocessorcoupled to said control panel and to said control circuit boardassembly, said microprocessor adapted to process signals from aplurality of devices providing water parameter information and toenergize said heater according to user preferences; a water presencesensor apparatus for detecting the presence of water in said heaterhousing element; a water temperature sensor apparatus for providingelectrical temperature signals to the controller indicative of watertemperature at separated first and second locations on or within saidheater housing or a combination thereof; and independent circuitapparatus connected to said water temperature sensor apparatus and tosaid at least one power switching device, said independent circuitapparatus for automatically causing the high voltage power to bedisconnected from the heater assembly when the water temperature exceedsa predetermined temperature, said independent circuit apparatusrequiring a manual reset once the water temperature has dropped below apredetermined level to allow the high voltage power to be reconnected tothe heater assembly.
 19. A system according to claim 18, wherein thetemperature sensor apparatus includes a first temperature sensor forsensing a first water temperature at a first location and a secondtemperature sensor for sensing a second water temperature sensor at asecond location, wherein said independent circuit apparatus includes afirst separate circuit responsive to the first temperature sensor fordisconnecting the heater when the first temperature exceeds saidpredetermined temperature, and a second separate circuit responsive tothe second temperature sensor for disconnecting the heater when thesecond temperature exceeds said predetermined temperature.
 20. A systemaccording to claim 18 with a second water pump or an air blowerconnected to said control circuit board assembly, said first pumpactivated whenever said second pump or air blower is activated.
 21. Asystem according to claim 20 wherein said second pump or said air bloweris deactivated whenever said water temperature exceeds a certain amount.22. A heating and control system for bathers, comprising: a controlcircuit board assembly comprising at least one power switching device; ahigh voltage power supply connected to control circuit board assembly; aheater assembly including a heater housing and heater element, saidheater element connected to said control circuit board assembly; amicroprocessor adapted to process signals from a plurality of inputdevices providing information regarding water parameters and to energizesaid heater according to user preference; a water temperature sensorapparatus for providing electrical temperature signals to themicroprocessor indicative of water temperature at separated first andsecond locations on or within said heater housing or a combinationthereof; independent circuit apparatus separate from said microprocessorand connected to the water temperature sensor apparatus and connected toat least one power switching device in the control circuit boardassembly; said independent circuit apparatus automatically causing thehigh power supply to be disconnected from the heater assembly when thetemperature exceeds a predetermined temperature, said circuit apparatusrequiring a manual reset once the temperature has dropped below apredetermined level.
 23. A system according to claim 22, wherein thetemperature sensor apparatus include a first temperature sensor forsensing a first water temperature at a first location and a secondtemperature sensor for sensing a second water temperature sensor at asecond location, and wherein the independent circuit apparatus includinga first separate circuit responsive to the first temperature sensor fordisconnecting the heater when the first temperature exceeds saidpredetermined temperature, and a second separate circuit responsive tothe second temperature sensor for disconnecting the heater when thesecond temperature exceeds said predetermined temperature.
 24. A systemaccording to claim 22 including a control panel mounted within useraccess on the spa, said control panel containing a user-activated deviceto activate a reset of said independent circuit apparatus.
 25. A spaincluding a heating and control system for bathers, comprising: acontrol circuit board assembly; a high voltage power supply connected tothe control circuit board assembly; a heater assembly connected to thecontrol circuit board assembly; water presence sensor apparatus todetermine the presence of water within the heater assembly; a pump forcirculating water through said heater assembly; at least one temperaturesensor for generating an electrical signal proportional to watertemperature located at said heater; an electronic controller adapted toselectively activate and deactivate said pump at selected timeintervals.
 26. A system according to claim 25 whereby said timeintervals are determined by calculating the rate of heat loss of thespa.
 27. A system according to claim 27 whereby said time intervals arevaried to minimize the number of sampling iterations of the pump.
 28. Asystem according to claim 25 whereby the pump is activated for a shortinterval of time, and then deactivated if the temperature of the wateris within a specified range of a selected temperature.
 29. A systemaccording to claim 25 wherein the electronic controller comprises amicroprocessor connected to the control circuit board assembly.
 30. Amethod for detecting the presence of water in a system including aheater element, a heater housing, and a microcomputer, the microcomputercontrolling the heater, at least one temperature sensor in closeproximity to the heater element, the temperature sensor feedingtemperature data to the microcomputer, the method comprising: collectingand storing a first temperature measurement value; activating the heaterelement for a predetermined time interval; deactivating the heaterelement for a selected time interval; collecting and storing a secondtemperature measurement value; calculating the difference between thefirst temperature measurement value and the second temperaturemeasurement value; comparing the resulting difference to a predeterminedvalue to establish the presence or absence of water adjacent the heaterelement.
 31. A method according to claim 30, wherein said at least onetemperature sensor includes first and second temperature transducers,and said first and second temperature values are respectively collectedfrom said first and second temperature transducers.
 32. A methodaccording to claim 31 wherein said first and second temperaturetransducers are in thermal contact with said heater housing.
 33. Amethod according to claim 30, further characterized in that the at leastone temperature sensor is in thermal contact with the heater housing.